1. Field of the Invention
The present invention relates to a silver halide photographic material and a method for processing the same, in particular, to a silver halide photographic material which may be processed with a processing solution having a pH of less than 11.0 to give a high-contrast negative image useful in a photomechanical process.
2. Prior Art
Various additives have been proposed for the purpose of improving photographic properties (e.g., sensitivity, antifogging property, rapid processability) of silver halide photographic materials.
Addition of hydrazine compounds to silver halide photographic emulsions and developers is known, for example, in U.S. Pat. No.3,730,727 (using a developer comprising ascorbic acid and a hydrazine compound in combination), U.S. Pat. No. 3,227,552 (using a hydrazine compound as an auxiliary developing agent for obtaining a direct positive color image), U.S. Pat. No. 3,386,831 (containing a .beta.-mono-phenylhydrazide of an aliphatic carboxylic acid as the stabilizer for silver halide photographic materials), U.S. Pat. No. 2,419,975, and Mees, The Theory of Photographic Process, 3rd Ed. (1966), page 281.
Of these, there is disclosed in U.S. Pat. No. 2,149,975 addition of hydrazine compounds to obtain hard negative images.
The U.S. Pat. No. 2,149,975, disclosing a silver halide photographic material containing a hydrazine compound as added to the silver chlorobromide emulsion therein, mentions that when the photographic material is processed with a high-pH developer having a pH of 12.8, an extremely hard photographic image having a gamma (.gamma.) value of more than 10 may be obtained. However, such a strongly-alkaline developer having a pH of nearly 13 is easily oxidized with air and is therefore unstable, so that it is not resistant to the storage or use for a long period of time.
Various modifications have been tried for processing a silver halide photographic material containing a hydrazine compound with a developer having a lower pH value to give a hard image.
JP-A-1-179939 and 1-179940 (the term "JP-A" as referred to herein means an "unexamined published Japanese patent application") have disclosed a method of processing a photographic material containing a nucleating development accelerator having a group adsorbing to silver halide emulsion grains and a nucleating agent also having a group adsorbing to the grains, with a developer having a pH of 11.0 or less. However, when the compound having an adsorbing group is added to silver halide emulsions in an amount exceeding a defined limit, it will detract from the light-sensitivity of the emulsions, or inhibit the developability thereof, or is harmful to other useful adsorbing additives. Therefore, the usable amount of the compound is limited so that even a photographic material containing the compound could not always express a sufficiently hard contrast.
In JP-A-60-140340 there is disclosed addition of amines to silver halide photographic materials to thereby elevate the hard contrast of the materials. However, when the materials are processed with a developer having a pH of less than 11.0, they could not express a sufficiently hard contrast.
In JP-A-56-106244 there is disclosed addition of amino compounds to developers having a pH of from 10 to 12 so as to elevate the contrast of the photographic materials processed therewith. However, the addition of amines to developers causes various problems that the developers come to emit offensive odors, the amines adhere to processing instruments to stain the processed materials and the wastes of the used developers cause environmental pollution. Therefore, it is desired to incorporate such amino compounds into photographic materials. However, photographic materials containing such amino compounds and providing sufficient advantages are not known up to the present.
In JP-A-61-167939 and 4-62544 there is disclosed addition of quaternary phosphonium salt compounds to developers to thereby elevate the hard contrast of the photographic materials processed therewith. However, the addition of such phosphonium salt compounds to developers caused a problem of environmental pollution. In addition, the contrast-elevating effect of the compounds is insufficient.
In JP-A-62-250439 and 62-280733 there is disclosed formation of hard images by processing photographic materials with developers having a pH of 11 or more and using hydrazine derivatives and quaternay onium salt compounds. Also in JP-A-61-47945, 61-47924, 1-179930 and 2-2542 there is disclosed formation of hard images by processing photographic materials with developers having a pH of 11 or more and using emulsions having a silver bromide content of 50 mol% or more and particular hydrazine compounds and quaternary onium salt compounds. However, since these use developers having a pH of 11 or more, the developers are easily oxidized with air and the properties of the processed photographic materials frequently vary due to the aging and fatigue of the developers being used.
In JP-A-4-51143, 4-56949 and 4-62544 there is disclosed processing of photographic materials containing particular hydrazine compounds along with amines, hydrazines and quaternary onium compounds, with developers having a pH of from 10.4 to 10.8.
Specifically, these laid-open specifications mention formation of hard images with .gamma. of 10 or more, using particular hydrazine derivatives and particular accelerators in silver iodobromide emulsion systems. However, the rate of development of photographic materials having such constitution is low so that the gradation of the processed materials becomes soft, the sensitivity thereof is varied and the Dmax value thereof is lowered due to the variation of the composition of the fatigued developers. Thus, the photographic materials processed with the developers, especially the fatigued developers, could not have sufficient photographic properties. In addition, since the dyes previously contained in photographic materials could not fully be dissolved out or decomposed during the development of the materials with the developers of the kind so that the dyes often remain in the processed photographic materials to cause so-called color stains. Thus, the photographic materials processed by the disclosed techniques could not be put to practical use.
In U.S. Pat. Nos. 4,998,604 and 4,994,365 there are disclosed hydrazine compounds having a repeating unit of ethylene oxide and hydrazine compounds having a pyridinium group. However, as is obvious from their examples, the contrast of the photographic materials using the disclosed compounds is not sufficient and it is difficult to obtain photographic materials having a hard contrast and a necessary Dmax in practical processing conditions even though the disclosed compounds are used.
The photographic properties of nucleating hard photographic materials using hydrazine derivatives greatly fluctuate, depending on the variation of the pH value of the developers used for processing them. The pH value of developers greatly fluctuates, due to aerial oxidation of them, etc. Precisely, it lowers when developers are oxidized with air or when they are thickened due to evaporation of water therefrom, and it rises when developers absorb carbon dioxide from air. Given the situation, various attempts have heretofore been made at reducing the dependence of photographic properties on the pH of developers. According to the prior art that is heretofore been developed, however, it is still impossible to obtain photographic materials having a sufficiently hard contrast even when processed with developers having a pH of 11 or less and those capable of giving high-quality images even when processed with fatigued developers.